Ordered Post Tags

readme.txt

=== Ordered Post Tags ===
Contributors: simonwheatley, cftp
Donate link: url
Tags: proof of concept, beta
Requires at least: 3.4.1
Tested up to: 3.4.1

This is a proof of concept plugin converting post tags into an ordered taxonomy.

== Description ==

This plugin is not recommended for production use as it overwrites a core taxonomy.

This is a proof of concept which shows how you might adapt the built-in Post Tags taxonomy so it can accept tags from the edit post UI and store/retrieve them in the specified order.

The plugin provides several template tags, they are similar enough to the core template tag equivalents without the "_ordered" suffix that you should be able to refer to the Codex for documentation; e.g. for `the_tags_ordered` refer to the documentation for `the_tags`.

ordered-post-tags-api.php

<?php

/*
Plugin Name: Ordered Post Tags – Template Tags & API
Plugin URI: https://gist.github.com/3217544
Description: Proof of concept plugin, not for production use. Provides template tags and an API for those functions. Won't work without Ordered Post Tags POC plugin.
Version: 0.1
Author: Simon Wheatley @ Code for the People Ltd
Author URI: http://codeforthepeople.com
*/

/**
 * Copyright 2012 Code for the People Ltd. All rights reserved
 * Released under the GPL license
 * http://www.opensource.org/licenses/gpl-license.php
 *
 * This is an add-on for WordPress
 * http://wordpress.org/
 *
 * **********************************************************************
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 * **********************************************************************
 */

// NOW SOME TEMPLATING FUNCTIONALITY FOR DEMO PURPOSES
// ===================================================

// N.B. Lots of duplicate code follows, were we to come to implement this in core
// it would be sensible to enhance the function equivalents of the functions
// below to accept an additional argument(s) to specify term_order.

/**
 * Retrieve the terms of the taxonomy that are attached to the post
 * in term_order.
 *
 * @param int $id Post ID.
 * @param string $taxonomy Taxonomy name.
 * @return array|bool False on failure. Array of term objects on success.
 */
function get_the_terms_ordered( $id, $taxonomy ) {
	global $post;

 	$id = (int) $id;

	if ( !$id ) {
		if ( empty( $post->ID ) )
			return false;
		else
			$id = (int) $post->ID;
	}

	$terms = get_object_term_cache( $id, $taxonomy );
	$terms = wp_cache_get($id, $taxonomy . '_ordered_relationships');
	if ( false === $terms ) {
		$terms = wp_get_object_terms( $id, $taxonomy, array( 'orderby' => 'term_order' ) );
		wp_cache_add($id, $terms, $taxonomy . '_ordered_relationships');
	}

	$terms = apply_filters( 'get_the_terms_ordered', $terms, $id, $taxonomy );

	if ( empty( $terms ) )
		return false;

	return $terms;
}

/**
 * Retrieve a post's terms as a list with specified format ordered by term_order.
 *
 * @param int $id Post ID.
 * @param string $taxonomy Taxonomy name.
 * @param string $before Optional. Before list.
 * @param string $sep Optional. Separate items using this.
 * @param string $after Optional. After list.
 * @return string
 */
function get_the_term_list_ordered( $id, $taxonomy, $before = '', $sep = '', $after = '' ) {
	$terms = get_the_terms_ordered( $id, $taxonomy );

	if ( is_wp_error( $terms ) )
		return $terms;

	if ( empty( $terms ) )
		return false;

	foreach ( $terms as $term ) {
		$link = get_term_link( $term, $taxonomy );
		if ( is_wp_error( $link ) )
			return $link;
		$term_links[] = '<a href="' . esc_url( $link ) . '" rel="tag">' . $term->name . '</a>';
	}

	$term_links = apply_filters( "term_links-$taxonomy", $term_links );

	return $before . join( $sep, $term_links ) . $after;
}

/**
 * Retrieve the tags for a post formatted as a string ordered by term_order.
 *
 * @uses apply_filters() Calls 'the_tags' filter on string list of tags.
 *
 * @param string $before Optional. Before tags.
 * @param string $sep Optional. Between tags.
 * @param string $after Optional. After tags.
 * @param int $id Optional. Post ID. Defaults to the current post.
 * @return string
 */
function get_the_tag_list_ordered( $before = '', $sep = '', $after = '', $id = 0 ) {
	return apply_filters( 'the_tags', get_the_term_list_ordered( $id, 'post_tag', $before, $sep, $after ), $before, $sep, $after, $id );
}

/**
 * Print the tags for a post in term_order.
 *
 *
 * @param string $before Optional. Before list.
 * @param string $sep Optional. Separate items using this.
 * @param string $after Optional. After list.
 * @return string
 */
function the_tags_ordered( $before = null, $sep = ', ', $after = '' ) {
	if ( null === $before )
		$before = __('Tags: ');
	echo get_the_tag_list_ordered($before, $sep, $after);
}


?>

ordered-post-tags.php

<?php

/*
Plugin Name: Ordered Post Tags
Plugin URI: https://gist.github.com/3217544
Description: Proof of concept plugin, not for production use. Converts post tags to an ordered taxonomy.
Version: 0.1
Author: Simon Wheatley @ Code for the People Ltd
Author URI: http://codeforthepeople.com
*/

/**
 * Copyright 2012 Code for the People Ltd. All rights reserved
 * Released under the GPL license
 * http://www.opensource.org/licenses/gpl-license.php
 *
 * This is an add-on for WordPress
 * http://wordpress.org/
 *
 * **********************************************************************
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 * **********************************************************************
 */

/**
 * Hooks the WordPress init action to interfere with the
  * post_tag taxonomy.
 *
 * @return void
 **/
function opt_init() {
	// Get the current args for the post_tag taxonomy
	$post_tag_tax = get_taxonomy( 'post_tag', ARRAY_A );
	// Convert to an array
	$post_tag_args = opt_convert_to_array( $post_tag_tax );
	// Now make it sortable
	$post_tag_args[ 'sort' ] = true;
	// Exploit a feature whereby you can overwrite a taxonomy :)
	register_taxonomy( 'post_tag', 'post', $post_tag_args );
}
add_action( 'init', 'opt_init' );

/**
 * A utility function that recursively traverses an object
 * and turns it into an associative array.
 *
 * @param mixed $thing Might be an object, might not be
 * @return array A (possibly multidimensional) array if an object (or array) was passed in
 **/
function opt_convert_to_array( & $thing ) {
	$thing = get_object_vars( $thing );
	if ( is_array( $thing ) )
		foreach ( $thing as $key => & $_thing )
			if ( is_object( $_thing ) )
				$thing[ $key ] = opt_convert_to_array( $_thing );
	return $thing;
}

?>